The subject matter disclosed herein relates to gasification systems and processes. More particularly, the subject matter relates to removal of particulate layers from gasification system components.
Gasification is a process for the production of power, chemicals, and industrial gases from carbonaceous or hydrocarbon feedstocks such as coal, heavy oil, and petroleum coke. Gasification converts carbonaceous or hydrocarbon feedstocks into synthesis gas, also known as syngas, comprising primarily hydrogen and carbon monoxide. The resultant syngas is a feedstock for making useful organic compounds or can be used as a clean fuel to produce power.
In a typical gasification plant, a carbonaceous or hydrocarbon feedstock and molecular oxygen are contacted at high pressures within a partial oxidation reactor (gasifier). The feedstock and molecular oxygen react and form syngas. Non-gasifiable ash material and unconverted and/or incompletely converted feedstock are by products of the process and take essentially two forms: molten slag and smaller particles referred to as “fines”. In some gasification plants, a syngas cooler is located downstream of the gasifier. The syngas, ash, slag and fines cool as they travel through the syngas cooler. A quench process cools and saturates the syngas near the exit of the syngas cooler. Alternatively, in gasification plants without syngas coolers, the quench is located near the exit of the gasifier. Further, additional cooling and/or gas clean-up components may be disposed downstream of the quench. During the cooling process, however, deposits of soot and ash, for example, form on interior surfaces of the syngas cooler, and/or the quench and additional cooling components. The deposits in the syngas cooler create many problems. For example, the deposit layer prevents efficient heat transfer from taking place, resulting in a reduction in steam production from the gasification process. Also, deposits may include corrosive species, thus the removal of the corrosive deposits would prolong the life of components of the syngas cooler, for example, heat transfer tubes. Further, deposits often break off from the interior of the syngas cooler under some operating conditions, for example, startup and shutdown. Such spontaneous liberation of large deposits often results in plugging of downstream components of the syngas cooler. Finally, falling deposits create a hazard for workers performing maintenance and/or repairs in the syngas cooler. Therefore it is desirable to remove the deposits at regular intervals prior to the deposits developing into a substantial size.